provide a mechanism for dynamically pluggable backends

RB_ID=165245
make the list of enums lazy

RB_ID=165351
back out the include mapping hack

RB_ID=165354
fix included reference directories
update changelog
bump version to 3.3.1
Initial port of the apache java thrift generator to scrooge (does not yet have maven plugin integration, other notes in the README)

RB_ID=162745
tiny fixes to unbreak ci
Bump finagle to 6.5.2

RB_ID=166653
Ensure collections using enums serialize types as i32

RB_ID=166802
update changelog
bump version to 3.3.2
implement unions in the apache java version

RB_ID=166278
enable oneways

RB_ID=166400
cleanup compiler warnings

RB_ID=167469
add a benchmark suite and framework for experimenting

RB_ID=167420
fix broken tests
Add proper hashcode method for science.

RB_ID=167936
Remove the tracerFactory usage and use tracer instead.

RB_ID=168094
let people know